Biological properties of surface modified 316 LVM steel

This paper aimed to investigate the selected physicochemical and biological properties of titanium dioxide thin films deposited by atomic layer deposition on 316LVM stainless steel dedicated for cardiovascular implants. The main challenge in surface modification of these implants is the complexity of the processes taking place in the circulatory system. The atomic layer deposition was carried out for a number of cycles 500 and temperature 200 °C for 316LVM stainless steel substrate. The surface topography and surface microstructure were examined. Mouse fibroblasts L929 and Human Dermal Fibroblasts (NHDF-Ad) were used for cytotoxicity assays. The following biocompatibility aspects were investigated in vitro: direct cytotoxicity, hemolysis, platelet activation and aggregation, and pro-inflammatory cytokine levels. The titanium dioxide thin films inherited the substrate topography. The surface microstructure was amorphous with the typical layer by layer growth. The film improved the in vitro cell response in terms of cell viability. The cells were also able to proliferate and adhere; however, differences in the cell morphology and the distribution of cell nuclei were observed. The host cell damage was not noted in terms of lactate dehydrogenase levels. The proposed surface modification reduced the hemolysis index and did not significantly affect platelet activation and aggregation. Acute cytotoxicity of the thin films is not predicted basing on the in vitro pro-inflammatory cytokine assay. The results of the biological tests may be basis for further biological assessment proving the full biocompatibility of the proposed surface modification dedicated for specific cardiovascular implants.